This study will evaluate the relative efficacy of two postoperative treatment regimens in patients with Dukes' B and C carcinoma of the colon: 1). 5-fluorocil (f-Fu)+ Leucovorin. LV delivered for 5 consecutive days on a 28 day schedule for 6 cycles and 2). 5-Fu + LV delivered for 5 consecutive days plus interferon Alfa-2 on a 28 day schedule for 6 cycles. For both treatment groups, regardless of delays or interruptions of therapy, a new cycle should not be started beyond 6 months from the initiation protocol therapy.